The Science of Summer

Summer is on the way and our team in the Dallas Arboretum Rory Meyers Children’s Adventure Garden is eager to share some of the magic behind the season! Have you ever wondered how we decide when spring ends and summer begins? Rather than just the temperature, seasons change based on the length of days. As the tilt of the Earth positions the Northern Hemisphere (where we live!) toward the sun, the days get longer.

The days continue to get longer until the sun is aligned directly over the Tropic of Cancer, which passes through Central America. The longest day of the year in the Northern Hemisphere is what we call the Summer Solstice and marks the first day of summer! On this day, the sun will stay high in the sky for longer than any other day. In 2018, the Summer Solstice takes place on June 21, when the sun will rise at 6:19 AM and set at 8:38 PM. That’s a total of 14 hours and 19 minutes!

Since the sun shines for so long on the Summer Solstice, you might think that it’s also the hottest day of the year. However, the hottest days of summer come weeks after the Summer Solstice when the oceans absorb lots heat from the sun. If you have ever jumped in a swimming pool on a hot day, you probably noticed the temperature of the water is cooler than the air. The pool is cooler because water changes temperature more slowly than the air in the atmosphere. Just like a giant pool, oceans take a longer time to warm up than the atmosphere. On the first day of summer the ocean is still warming up. A few weeks later, the ocean is warmed to its peak and the hottest days of the year begin! This phenomenon is described as “seasonal temperature lag.”

If you’d like to track the seasons with us at the Rory Meyers Children’s Adventure Garden, you can visit our Energy Tower to observe indicators of where the sun rises and falls on each solstice and equinox in the year. Don’t forget to visit the OmniGlobe Theater in the Exploration Center for an out-of-this-world view of Earth and our place in the Solar System!